Gaia DR3 and nearby galaxies: where do foregrounds matter?

ABSTRACT Nearby galaxies provide populations of stellar and non-stellar sources at a common distance in quantifiable environments. All are observed through the Milky Way foreground, with varying degrees contamination that depend on Galactic latitude size target galaxy. This work uses Gaia Data Release 3 (DR3) to identify foreground via astrometric measurements thus quantify for large sample nearby galaxies. There approximately half million directions 1401 listed Local Volume Galaxy catalogue (D < 11 Mpc), excluding largest Group About two-thirds have properties consistent sources; these brighter, redder, less centrally concentrated than non-foreground sources. Averaged over galaxies, make up 50 per cent projected radius r50 = 1.06a26, where a26 is angular diameter B 26.5 isophote. Foreground apparent magnitude mG, 20.50. limit corresponds tip red giant branch absolute D 450 kpc, globular cluster luminosity function peak 5 Mpc. data powerful tool removing population studies although removal will be incomplete beyond distances